1. Field of the Invention
The present invention relates to a charged particle beam writing apparatus and a charged particle beam writing method, for example, a measuring procedure or a using method for a surface height level of a target object when a writing position is corrected at the surface height level and a writing apparatus which includes a multicolumn for measuring a surface height level of a target object.
2. Related Art
A lithography technique which bears the advance of micropatterning of a semiconductor device is only a very important process which generates a pattern in semiconductor manufacturing processes. In recent years, with a high degree of integration of an LSI, a circuit line width required for a semiconductor device is miniaturized every year. In order to form a desired circuit pattern to the semiconductor device, a high-precision original pattern (also called a reticle or a mask) is necessary. In this case, an electron beam writing technique inherently has an excellent resolution and is used in production of a high-precision original pattern.
FIG. 14 is a conceptual diagram for explaining an operation of a variable shaping electron beam writing apparatus.
The variable shaping electron beam (EB) writing apparatus operates as described below. In a first aperture 410, an oblong (for example, rectangular) opening 411 to shape an electron beam 330 is formed. In a second aperture 420, a variable shaping opening 421 to shape the electron beam 330 passing through the rectangular opening 411 into a desired oblong shape is formed. The electron beam 330 irradiated from a charged particle source 430 and passing through the rectangular opening 411 is deflected by a deflector. The electron beam 330 passes through a part of the variable shaping opening 421 and is irradiated on a target object placed on a stage. The stage continuously moves in a predetermined direction (for example, an X direction). In this manner, an oblong shape which can pass through both the opening 411 and the variable shaping opening 421 is written in a writing region of the target object 340. A scheme which causes an electron beam to pass through both the rectangular opening 411 and the variable shaping opening 421 to form an arbitrary shape is called a variable shaping scheme.
In this case, in the electron beam writing apparatus, a writing position changes depending on the height of a target object surface of a mask or a wafer. For this reason, a height (z) is required to be measured to correct the position depending on the measured value. For example, the height of the entire mask is measured in advance before the pattern writing, and pattern writing is performed while correcting the position depending on the value (for example, see Japanese Patent No. 3277746). Alternatively, height data is obtained while performing pattern writing, and the pattern writing is performed on real time by using the value while performing correction.
A writing apparatus using a multicolumn cell (MCC) scheme achieved by incorporating two or more optical system columns in one electron lens barrel is developed. The columns are arranged in the same writing condition, and each of the columns performs variable-shaped pattern writing (for example, see “Yasuda Hiroshi, Haraguchi Takeshi, et al., “multicolumn cell MCC-PoC (Proof of concept) system evaluation”, 3rd symposium of charged particle optics, pp. 125 to 128, Sep. 18 to 19, 2003”, “T. Haraguchi, T. Sakazaki, S. Hamaguchi and H. Yasuda, “Development of electromagnetic lenses for multielectron beam lithography system”, 2726, J. Vac. Sci. Technol. B20 (6), November/December 2002”, or “T. Haraguchi, T. Sakazaki, T. Satoh, M. Nakano, S. Hamaguchi, T. Kiuchi, H. Yabara and H. Yasuda, “Multicolumn cell: Evaluation of the proof of concept system”, 985, J. Vac. Sci. Technol. B22 (3), May/June 2004”).
As described above, there is a method of measuring a height in advance. However, when a height is measured in advance, the measurement time directly generates a loss time to make a writing time longer. When correction is performed on real time in a writing apparatus including a multicolumn, height measurers (z sensors) the number of which is equal to the number of columns are necessary. In this case, the manufacturing cost of the apparatus disadvantageously increases. Furthermore, in order to mount a large number of z sensors, it is difficult to reduce the z sensors in size.